As a learning support assistant for adults with learning disabilities I know that I cannot use my own intellectual gifts as a standard by which to evaluate and judge the work of the students I assist in the classroom.
This pointed me to a more general insight into the limitations of self-knowledge in grasping the motives and sensibilities of other people.
The role of empathetic or emotional intelligence is precisely to help one along in evaluating others as they are and as they stand, with their own personality preferences, their own sensibilities, their own temperaments, their own likes and dislikes, their own social and intellectual backgrounds, their own financial resources etc.
To close the circle of this argument I would make the case that true self-knowledge includes the ability for empathy, i.e. the capacity to perceive the difference in perception or, if you will, wavelength that lies between you and others around you.
This definition of empathy as perceiving the world through other people's eyes and therefore also the difference in the ways you see it was reached in a most early blog post on ScruffyOwlet's Tree, A Brief Anatomy of Perception.
It is empathy that allows one to reach to others despite your differences and as someone said
"It is not our differences that divide us but our inability to celebrate those differences."